How long does the engine run at idle until you get into overheating? The car may have got by on a poor fan coupling when in actual use. Yet when sitting still the fluid coupling does not engage enough and the engine coolant gets too hot. The fan blast could be very weak.

Check for the presence of the fans fluid coupling. I would think the easiest test would be to get the engine to the normal operating temperature and see if you can manually fairly easily spin the fan blades as soon as you shut down. I have never done this test but to me the blades should be pretty well locked up. Or at least very hard to turn in comparison to when the engine was cold.

Other members may have a better approach. Plus if the lockup also need the unit to be spinning my test would be invalid. Even cold though the fan should not pretty much freewheel though.

I also wondered about the normally closed nipple on the injector return ingesting air and showing up in the output of the injection pump? My feeling is you should have seen fuel leakage there rather than air intake.

My problem is does this mean something or not? I feel I am missing something here although it might be normal it does not sound to me like it is. There instead should have been a modest fluid pressure output. Yet again I am not sure.

Normally if the fuel pressure provided to the injection pump is enough to keep the relief valve semi open. The fuel return system is under a very modest return pressure. In a properly operating system you should always have some output from the injection pumps relief valve.

Another possible observation is you may have a true grey market car with a European version injection pump. Many of those did not have a cigar hose although it will not hurt to incorporate one. These cars sold in north America had a different injection pump than those sold in Europe.

You explained your disability well. I am trying to keep this in mind as I post this. I will try to give some thought to you overall problems with this car over the next few days. I hope members more knowledgeable than myself will continue to help as well.

Confusion erupts in even so called normal minds. Compound this with a disability and it must be very frustrating. I do not want you to grasp at any straws I may post. Better if other members look at them and reinforce them when they think they might have some validity or merit first.

You have been pretty lucky as when the oil pan was damaged it is possible the engine lost oil pressure as you registered none on the gauge when cranking. Until you repaired the damage.

These engines normally sit with an oil pressure gauge initially at three when cold. Generally dropping off to between 1 and 2 at normal operating temperatures. Do you remember what oil pressure you have at about 80C or 170F?

Good to hear you put the clear hose in. Yes, you have an air leak if the fuel drains out of it overnight. Is it still draining after you fixed the cap on the 5th injector return nipple? If not, you have a leak elsewhere, which could be anywhere in the fuel system. Some common hard to find leak points are rusty pin holes in the metal fuel supply line under the car, which are often hidden. It does not usually drip fuel because it is under a clamp with a rubber sleeve over it. If you remove the clamp and it looks damp and smells of diesel it is leaking.

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85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

Yes. Take the banjo bolt out and take it apart and stretch the spring to 27 mm. 14 & 17 mm wrench. Don't lose the copper washer and the ball.

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85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

Thanks for the input.

I did bleed the cooling system using a pressure tester. I hope it was sufficient. Also replaced the thermostat at the same time. In any event. I keep a close eye on the gauge.

It does not seem to be overheating now, at least not while sitting in the driveway. Under load may tell a different tale, but for now I am tilting at different windmills. I will look further into it when I get the low power issue resolved.

Fluid-coupled fans can be tricky to diagnose, but I am pretty sure this one is working properly. I wll know better when I get it running better and in the meantime I will keep a close eye on the temperature. Fortunately Mercedes built these things like a tank and they do not blow headgaskets at the drop of a hat. There is a lot to be said for German durability.

I was a bit flummoxed by that as well. There was no leakage I could detect from that plug hose. But in the end it looks like that was it. I do need to inspect for air bleeding in overnight though. It does crank too long before firing. That could be the reason. I also will be making a fuel pressure tap out of a banjo bolt so I can measure the pressure at idle and running. I will also check fuel volume (just as important as pressure!) at the same time.

I am a bit puzzled about the cigar hose. As I understand it, the car will run fine without it. In any case I have replaced it with a clear hose so I can see what is going on as far as air bubbles in they system is concerned. I do have a new one to put in once I get things worked out.

Can anyone tell me more about what the cigar hose does and whether it is needed? I know it is supposed to smooth out the fuel pulses but I don't know why that is so important. Or is it?

I have learned how to tell when I need to stop working on something because I am chasing my tail. That is why this has taken so long. That and I forget that I have this project.... but now that it is parked in front of the house instead of down in a remote corner of the property I am forced to look at it every day. That should get it running sooner.

Fortunately I am pretty good at sifting through things to determine if it would send me down a rabbit hole or not. It takes a few days sometimes but I seem to be doing OK on that score.

By the look of the pan I am pretty confident that it was damaged right before it stopped running. The scrapes in the damaged area are not all filled in with dirty oil, it looks like she was pulled off the side of the road and hit a rock (there is clearly sandstone in the wound) when she was pulling off the road. Also there was absolutely no sign of any damage when I had the pan off. No metal flakes or anything like that.

It is claimed that 1/8" Viton hose is best for the injector return hoses. I just put on my 1985 300D because the woven hoses were leaking pretty bad (~4 yrs old, but using Diesel HPR). I bought 10 ft for $19 on ebay from China. Can't tell if truly Viton, but has held up for 2 weeks so far. I tried a little silicone hose and it started swelling and leaking in 2 days.

I also have seen the dash gage go high after a coolant change, even pegging at 120 C. But, I don't think the whole engine got so hot. I think when you have an air pocket, the sensor sees hot vapor. Once I added more coolant (tank had dropped) it ran OK. If you installed the thermostat correctly w/ the little vent hole up, the air should eventually purge out, assuming the little copper rattle pin move freely to keep the hole open.

You could test the clutch-fan like Ed China did on Wheeler Dealers. He grabbed it on an idling engine w/ a leather glove and said if it was good he wouldn't be able to hold it. The true metric is to count your fingers before and after this test and subtract. 5 missing fingers = excellent fan clutch.

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1984 & 1985 CA 300D's
1964 & 65 Mopar's - Valiant, Dart, Newport
1996 & 2002 Chrysler minivans